Radio apparatus



July 23, 1929. w rn c; 1,722,068

RADIO APPARATUS Filed Nov. 4, 1924 //2 venf'or flona/d f." Wh/fing.

by ZJW my.

Patented July 23, 1929.

UNITED STATES PATENT OFFICE;

DONALD F. WHITING, OF NEW YORK, N. Y., ASSIGNOR TO WESTERN ELECTRIC COM- IEANY, INCORPORATEJI'OF NEW YORK, N.-'Y., A CORPORATION OF NEW YORK.

RADIO APPARATUS.

Application filed November 4, 1924. Serial No. 747,704.

the tuning in a radio receiving set. Another object is to provide more efficient regeneration in a radio receiving set.

A feature of the invention is a three-coil transformer comprising windings having low distributed capacity which for convenience are represented in the attached" drawing as the type commonly called honeycomb coils angularly disposed forming substantially three sides of a triangle so that each coil is in inductive relation to the other two coils. I

In regenerative circuits of the type heretofore generally used having a three-coil transformer, the third coil, commonly called the tickler coil, connected in the plate circuit of the space discharge device is placed in inductive relationship to the secondary which is connected in the grid-filament circuit of the device. The purpose of this coil is to feed back energy into the secondary circuit from the plate circuit to partly compensate for the energy lost due to the effective resistance of the coils and the space discharge device. This feed-back of energy has the effect of the introduction of negative resistance which'is added to the secondary circuit; in such an amount that it will compensate, or nearly compensate,.for the positive resistance of that circuit. When the condition is reached wherein the negative resistance is' ance the circuit becomes unstable and is in an oscillating condition as any current applied would continue flowing or tend to build; up indefinitely. The disadvantage of this type of coupling is that the amount of feedback which it is possibleto obtain without bringing the circuit into an oscillating state is limited to that necessary to overcome the secondary losses which are small in respect to the primary losses. Furthermore, the effect of the feed-back reaching the primary circuit, in which the losses are the greaterand the tuning broad due to the antenna, ground and radiation resistances, is to introduce additional positive resistance into this circuit which adds to these losses and broadens'the tuning further. i

7 By means of' the transformer described inv connection with this invention, regeneration is accomplished by magnetic coupling between the tickler coil and the primary circuit, as well as between the tickler coil and the secondary circuit. The negative resistance which is added to theprimary circuitby this method will reduce the total resistances. and thereby decrease the losses an'd increase the sharpness of tuningin that circuit; Consequently, as it is not necessary to feed back as much energy into the secondary circuitv as heretofore, the negative resistance of this circuit will be numerically less than the positive resistance and it will not reach an oscil lating condition. i

Although the novel features which are believed to be characteristic of this invention will be pointedout with particularity in the claims appended hereto, the invention itself, 1ts ob ects and advantages, the mode of its operation and details of its organization will be better understood by referring to the fol lowing description taken in connection with the accompanying drawing in which Fig. 1 is a plan View of the type of three coil transformer heretofore generally used in regenerating circuits; Fig. 2 is a plan view of one.

type of transformer embodying this invention; Fig. 3 is a plan view of a more practical form of transformer embodying this invention and Fig. a shows diagrammatically a circuit in which this used.

.In Fig. 1 the primary coil2 and the secondary coil 3 are placed in inductive relationship to one another and the feed-backor tickler coil 4 is placed in inductive relationship to coils 2 and 3 in the manner heretofore generally used. If high frequency currentsflow ing in the windings of primary coil 2 inducea magnetic flux in the direction indicated the dotted arrow associated with coil 2, the effect of a portion of this flux passingthrough secondary coil 3 will be toinduce currents in the windingsof coil 3 insuch a direction that the flux induced by these currentsv will be in the direction indicated by the dotted arrow transformer may be associated with coil 3 which, it should be I "3 by the action of the flux of tickler coil 4,

it is obvious that the flux ofcoil 4 must pass through coil 3 in a similar direction to that taken by the flux from coil 2; that is, opposed to the direction of the flux of coil 8. There fore the dotted arrow associated with coil 4 indicates the direction of the flux induced by the currents initially flowing in coil 2, the effect of the fluxof coil 4 upon coil 2 will tend to induce-currents in the windings of coil 2 in a direction opposite to those initially flowing therein, and the result will be a reduction of the value of the resultant current. If the positions of any of the coils are interchanged the same relationship hold; and, if the direc' tion of the'current flowing in the windings of coil 4 be reversed, the efiect will be that the currents flowing in primary coil 2 will be aug-,

merited while the'currents-flowing in secondary coll 3 W111 be reduced. It therefore follows that with this more or less parallel. are

rangement of the coils the benefits accruing through regeneration can occur in either the primary or the secondary circuits, but never in both, the other circuit being affected detrimentally. V

' In Fig. 2 which shows one form of the presentinvention, theprimary coil 2, secondary coil 3 and tickler coil 4 are arranged in triangular relationship with their axes'displaced at an angle of from one another and meeting at a common central point. The directions of the magnetic fluxes induced by currents flowing in the windings of the coilsare represented by arrows associated with the respective coils. Owing to the nearly opposing directions of llllGflLlXGS it is apparent that the flux set up by currents flowing in any one of the coils induces currents in'the remaining two coils which are in the same direction as the currents originally flowing in these coils and, therefore, augment the currents in both coils simultaneously, in contrast to the effects resulting from the arrangement of Fig. 1. i

1 Owing to the condition that the number of turns in the winding of primary coil 2 is' usually less than those in the'windingsof secondary: coil 3 and also to the condition that the losses existing in the primary circuit are greater than those present in the secondary circuit, it is usually advisable to place primary coil 2 in closer inductive relation to V tickler coil 4 than that existing between secondary coil 3 and tickler coil 4. It has also been found-thatwhen this type of transform: er-is used the coupling'required between pri-' mary ,coil 2 and secondary coil '3 for most successful operation is considerably less than that which is desirable when an arrangement like.

that of 1 is used. I V v 'Fig. 3 shows arrangement of the coils in which these conditions have been satisfied and this constitutes one practical form which the invention may take. Primary coil 2 is in close inductive relationship with tickler coil 4, whereas the coupling between secon dary coil 3 and each of the other two coils is relatively Weak. It can be seen from the opposing directions of the arrows that the directions of the fluxes are similar to those of Fig. 2 and that the action is the same.

' In'Fig. 4 the-antenna circuit comprising antenna 1, primary coil 2 of receiving transformer 5 and'variable condenser 6 is loosely and variably coupled to the secondary circuit by means of the secondary 3 of the receiving transformer. The tuned secondary circuit consists of secondary 3 and variable condenser 8, which is adapted to be adjusted to bring the circuit into resonance with the incoming waves. The energy in this circuit is amplified in a radio frequency amplifier comprising space discharge device 7' having its input circuit connected across condenser 8 and its output or plate circuit connected to the primary 9 of radio frequency transformer 10. Secon dary 11 of this transformer is connectedin the" input circuit of the second space discharge device 12 which is adapted to operate as a detcctor. The output or plate circuit of this second space discharge device 12 includes a coil 4 in inductive relationship to both primarycoil 2 and secondary coil 3 and the primary of audio frequency transformer 13. The secondary of transfcrmer13 is included in the input circuit of the first space discharge device 7, in which the audio frequency energy from the detector 12 is amplified. Receiver 14, herein shown as a loud speaking horn, although it may takeany other form desired, is included in the plate circuit of this amplifier 7 and transforms the audio frequency energy into sound waves.

Space current and filament heating curquency impulses received in; the antenna ciri v cuit are transferred to the.v input circuit of the radio frequency amplifier 7 by means of transformer 5 and are amplif ed inthis tube. The amplified signals are then impressediupon tube 12, 'a portion of the output energy of which consists of audiofrequency energy brought about by the detector action of the tube and another portion of which is similar to the impressed signals exceptthat it isin amplified form. This high frequency com-' ponent of the energy in the plate'circuit' is then impressed upon both the primary and the secondary coils of transformer 5 by means of feed-back coil 4 thereby increasing the amount of energy flowing in the antenna circuit and further strengthening the signals rcceived. At the same time the energy flowing in the secondary circuit will be increased directly by transfer between coils 4 and 3 and also indirectly by transfer between coils 4, 2 and 3. The coupling between tickler coil 4 and the secondary coil 3 is much looser than that between the ti'ckler coil and the primary 2, in order that the negative resistance of the secondary circuit will not be increased to such an extent that the operation will become unstable, when the resistances of the primary circuit are reduced to the optimumvalue. The advantage of this will be apparent when it is remembered that the secondary circuit is ordinarily of low loss, or high time constant, whereas the primary circuit is of high loss, or low time constant. A comparatively small amount of energy fed back into the secondary circuit would tend to produce unstable operation, as above set forth, whereas a much larger amount of energy fed back into'the primary circuit would only tend to increase the signal strength and would not cause the operation of the circuit to become unstable. The low frequency component of the energy in the plate circuit of tube 12 is impressed upon the grid-filament circuit of tube 7 by audio frequency transformer 13, where it is repeated and amplified before operatin a sound reproducing means 14. Although t is circuit has been shown as a reflex regenerative circuit by way of illustration, the transformer arrangement 5 is equally applicable to a single tube receiver wherein the tube operates as a detector only, or to any other transformer coupled circuit in which regeneration is made use of to reduce the losses in the primary or secondary circuits or to increase the selectivity of the system.

Although the coils composing the transformer 5 have been shown in Figs. 2, 3 and 4 as honeycomb coils, theinvention is not limited thereto, but is equally applicable to other coils wound in a different manner, which may be mounted in the same general relationship.

What is claimed is:

1. A regenerative radio receiver comprising a plurality of space discharge devices connected in tandem, a wave receiving circuit, an input circuit for the first of said space discharge devices and an'output circuit for the last device, and means for inductively coupling said output circuit additively to said wave receiving circuit and said input circuit in such a manner that more energy is transferred from said output circuit to said Wave receiving circuit than to said input circuit.

2. A regenerative radio receiver comprising a wave receiving circuit, a plurality of space discharge devices connected in tandem, an input circuit for the first of said space discharge devices, and an output circuit for the last device, coils in each said wave receiving circuit, said input circuit and said output circuit, and means for inductively coupling said coils additively, whereby the amount of energy transferred from said output circuit coil to said wave receiving circuit coil is greater fihan that transferred to said input circuit 001 3. A regenerative radio receiver comprising a wave receiving circuit consisting of an antenna, an inductance coil, a variable condenser and a ground connection; a plurality of space discharge devices connected in tandem, an input circuit for the first of said space discharge devices and an output circuit for the last device, a coil in each said input circuit and said output circuit, means for inductively coupling said coils additively, in such a manner that more energy is transferred from said output circuit coil to said wave receiving circuit coil than to said input circuit coil.

In witness whereof, I hereunto subscribe my name this 30th day of October A. D., 1924.

DONALD F. WHITING. 

